Michelson-Morley Experiment Flashcards
(10 cards)
What is absolute motion and how was it related to the concept of the ether?
Absolute motion is the idea that all movement occurs relative to a fixed medium called the ether, which was once believed to permeate the entire universe and act as the medium through which light waves propagate.
What was the primary aim of the Michelson-Morley experiment?
To detect the Earth’s absolute motion through the ether by measuring differences in the speed of light in perpendicular directions.
What apparatus did Michelson and Morley use in their experiment, and what is it called?
They used an interferometer, which consisted of a beam splitter (partially reflective surface), a compensating glass block, and two mirrors arranged to split and recombine light beams travelling perpendicular paths.
What is the function of the beam splitter in the Michelson-Morley interferometer?
It partially reflects light and partially transmits it, splitting the light into two beams that travel at 90° angles to each other.
Why is a glass block (compensating plate) used in the Michelson-Morley interferometer?
To ensure both light beams travel through the same amount of glass so any optical path differences are due to motion, not materials.
According to the ether theory, what result was expected when the interferometer was rotated?
A shift in the interference pattern due to the light beam travelling parallel to the Earth’s motion taking longer than the one travelling perpendicular.
What was the actual observation in the Michelson-Morley experiment?
No shift in the interference pattern occurred when the apparatus was rotated.
What does the absence of an interference pattern shift suggest?
That the time taken for light to travel was unaffected by the direction of motion or rotation of the apparatus, contradicting the ether theory.
What is the first possible conclusion drawn from the Michelson-Morley null result?
The ether does not exist or the Earth drags the ether with it, making its motion undetectable.
What is the second major conclusion from the Michelson-Morley experiment?
The speed of light is invariant in free space — it is the same regardless of the motion of the source or observer.
